Isomerization of neohexene

ABSTRACT

NEOHEXENE IS SKELETALLY ISOMERIZED TO 2,3-DIMETHYLBUTENE-2 WITH EXCELLENT SELECTIVITY AND CONVERSION UTILIZING AN ALUMINA CATALYST CONTAINING 0.1 TO 0.2 WEIGHT PERCENT SODIUM OXIDE AND HAVING A SURFACE AREA OF 150 TO 180 SQUARE METERS PER GRAM. 2,3-DIMETHYLBUTENE-1 PRODUCED IN THE REACTION IS DOUBLE BOND-ISOMERIZED TO PROVIDE ADDITIONAL 2,3-DEMETHYLBUTENE-2. WHERE THE NEOHEXENE IS PRODUCED BY DISPROPORTIONATION OF 2,4,4-TRIMETHYLPENTENE-2 AND ETHYLENE, A DIMETHYLBUTENE-1 FRACTION CONTAINING METHYLPENTENES FROM THE SECOND ISOMERIZATION STEP CAN BE ADVANTAGEOUSLY FED TO THE DISPROPORTIONATION CATALYST ZONE, THEREBY ELIMINATING THE PROBLEM OF SEPARATING THE METHYLPENTENES.

Dec. 25, 1973 J. w. MYERS ISOMERIZATION OF NEOHEXENE Filed Dec. 6, 1971 MZMSE FUDQONEN NN MW NZmPDmlI BNOZ Nouvzluawosl oNoa 319000 o/A/LL E25 @mw INVENTOR.

J. w. MYERS 'Afro/Mfrs la. UU B DQO United States Patent O 3,781,377 ISOMERIZATION F NEOHEXENE John W. Myers, Bartlesville, Okla., assignor to Phillips Petroleum Company Continuation-in-part of abandoned application Ser. No.

859,815, Sept. 22, 1969. This application Dec. 6, 1971,

Ser. No. 205,377

Int. Cl. C07c 5 /24 U.S. Cl. 260-683.2 11 Claims ABSTRACT 0F THE DISCLOSURE 'I'his applicationis a continuation-in-part of U.S. application Ser. No. 859,815 led Sept. 22, 1969, now abandoned.

BRIEF STATEMENT OF THE INVENTION Heretofore, neohexene, i.e., 3,3-dimethylbutene-l, has been converted to 2,3-dimethylbutene-2 by contacting it with alumina having surface areas of the order of 75 to 85 square meters per gram and containing 0.4 to 0.5 weight percent sodium oxide. When operating under skeletal isomerization conditions, either the selectivity or conversion was low. Thus, employing conditions suitable for obtaining selectivities above 90 percent, conversions of 80 percent or less were realized. Conversely, when employing conditions suitable for obtaining conversions above 90 percent, the selectivity dropped well below 80 percent.

I have discovered that high conversions and selectivity can be simultaneously realized by utilizing an alumina of low sodium oxide content and high surface area. Specically, where the alumina has a sodium oxide content of 0.1 -to 0.2 and a surface area of 150 to 180 square meters per gram, the isomerization occurs with selectivity and conversion both above 90 percent over a wide range of operating conditions. Presently preferred is a gamma alumina.

In another aspect, I have provided a process for producing a high yield of 2,3-dimethylbutene-2 from neohexene by a novel combination of skeletal and double bond isomerization steps and related fractionation steps. This process is applicable broadly to the conversion of neohexene with any of the well known skeletal isomerization catalysts, and involves double bond isomerization of the by-product, 2,3-dimethylbutene-l, to the desired product.

Where the neohexene is produced by disproportionation of 2,4,4-trimethylpentene-2 Iand ethylene, the 2,3-dimethylbutene-l concentrate from the efluent of the double bond isomerization -step can be advantageously fed to the disproportionation zone. lIn this fashion, I avoid separation of the methylpentenes present in the 2,3-dimethylbutene-l concentrate. 'I'hese materials are quite diflicult to separate by normal fractionation techniques.

The methylpentenes, when contacted with ethylene in the presence of an olefin disproportionation catalyst, are

3,781,377 Patented Dec. 25, 1973 substantially converted to lighter olens, such as isobutylene and propylene, which are easily separable. The dimethylbutenes are partly unconverted and partly converted to isobutylene. The isobutylene is valuable because it can be recovered easily and conventionally dimerized to 2,4,4-trimethylpentene and fed to the disproportionation reactor. Thus, the 2,3-dimethylbutene-l concentrate is substantially converted to isobutylene which is re-usable in the process and ultimately recovered as 2,3-dimethylbutene-2 product. Moreover, there is no undesirable buildup of methylpentenes because the methylpentenes are substantially converted to isobutylene which is useful to produce the 2,4,4-trimethylpentene.

DETAILED DESCRIPTION OF THE INVENTION The invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawing, in which:

The figure is a flow diagram of my novel isomerization and separation process.

Referring now to the figure, neohexene feed is charged through a conduit 10 to a skeletal isomerization zone 11 Where it is contacted with any of the well known skeletal isomerization catalysts at skeletal isomerization conditions. As previously noted, I have discovered that this isomerization takes place with an excellent combination of conversion and selectivity where the isomerization catalyst is alumina containing 0.1 to 0.2 weight percent sodium oxide, and having a surface area of to 180 square meters per gram, and more preferably a gamma alumina with such characteristics.

The effluent from the zone 11 is passed through a conduit 12 to a fractionation zone 13 wherefrom a 2,3-dimethylbutene-2 product is recovered through a conduit 14 and a 2,3-dimethylbutene-1 concentrate is recovered through a line 15. Hydrocarbon products having 5 or less carbon atoms are taken overhead through a line 16 and heavier products produced in the skeletal isomerization reactor are recovered as a bottoms product through the conduit 17.

In accordance with the invention, the 2,3-dimethylbutene-l concentrate, which contains small quantities of 2,3-dimethylbutene-2 and methylpentene, is fed to a double bond isomerization zone 18 utilizing any of the Well known double bond isomerization catalysts at double bond isomerization conditions. In this zone, a substantial portion of the 2,3dimethylbutene1 is converted to 2,3- dirnethylbutene-2. The latter component is recovered as a bottoms product from a fractionation zone 19 to which the eiuent of the reactor 18 is fed by a line 20, the product being recovered through a conduit 21 and combined with that discharged through the conduit 14.

The overhead product from the fractionation zone 19 consists mainly of 2,3dimethylbutene-l together with small quantities of methylpentenes and 2,3-dimethylbutene-2. In one aspect of the invention, part of this material, say 50 percent, is recovered through a valved conduit 22` and the remainder is passed through a valved line 23 to the inlet conduit of the zone 18. Where the quantity of methylpentenes produced is small, the process can advantageously be conduited 'as described for long periods of time without consequential build-up of methylpentenes in the system.

More advantageously, however, the neohexene feed charged to the conduit 10 is produced in a disproportionation catalyst zone 24, and the 2,3-dimethylbutene-1 stream taken overhead in the fractionation zone 19 is charge to the disproportionation zone through a valved conduit 25. Ethylene is charged to the disproportionation zone 24 through a line 26 and 2,4,4-trimethylpentene-2 is charged to the zone 24 through a conduit 27. In this In the broader aspects of the invention involving both fashion, a disproportionation reaction occurs between double bond and skeletal isomerization catalysts, other the ethylene and 2,4,4-trimethylpentene-2 to produce neoskeletal isomerization catalysts can be utilized in the zone hexene and isobutylene. The neohexene is recovered in a 11. Illustrative catalysts of this type are silica-alumina, lfractionation zone 28 and charged to the zone 11 through 5 eta-alumina, tungsten oxide or eta-alumina, molybdenathe conduit 10. Light products of the disproportionation boria-alumina, aluminum iiuoride, aluminum uoride reaction, principally isobutylene, are recovered from the promoted with oxides of tungsten, platinum, or chromium, zone 28 through a conduit 29 and heavy products are hydrogen @leidde-treated alumina, and the likerecovered through a conduit 30. The isobutylene is con- The catalyst in the double bond isomerization zone veniently dimerized (not shown) to form additional 2,4,4- 10 may be the Same aS that employed in the 2011 11 but trimethylpentene-Z for the ethylene disproportionation Operated under milder Conditions, aS indicated by tlie step. preceding table. Other suitable double bond isomerization According to the invention, a large portion of the meth. catalysts are 0.05 weight percent of palladium supported ylpentenes present in the conduit 25 are converted to pro- 0n alumina, batuXie, magnesium Oxide, Zine OXide, Phospylene and isobutylene in the zone 24. These products Pl101`ie acid 0n kieselguhf, and the likeare readily separated from the neohexene in the fractiona- Cata-lysis Suitable fOl' use in the dispropoftionation Step tion zone 28. A portion of the 2,3-dimethy1buteue-1 is are any of those catalyst systems which have activity for also disproportionated to isobutylene. This isobutylene is the conversion 0f an olefin into other similar olcns 0f added to that returned for dimerization. both higher and lower molecular Weight, such as the con- It will be apparent that I have achieved the objects of version of propylene into approximately equimolar quanthe invention providing a highly eflicient system for coniieS 0f ethylene and butenes- SPeCiiC examples are tung' verting neohexene to 2,3-dimethylbutene-2, involving the sten oxide on silica, molybdenum OXide 0n alumina, skeletal isomerization of the neohexene feed and double mOlybdenum OXidc 0n aluminum phosphate, rhenillm bond isomerization of 2,3-dimethylbuteene-1 produced in O'Xide 0n aluminum, and molybdenum heXaCafbOnyl 0n the skeletal isomerization step. The separation steps coalumina. A particularly preferred disproportionation cataoperate with the isomerization steps to provide eicient lyst system is one part of W03 on SiO2 catalyst in admixrecovery of the desired product. Where the neohexene ture with about 6 parts of MgO by weight. feed is provided by the disproportionation of ethylene It will be understood that the catalysts listed above and with 2,4,4-trirnethylpentene-2, the 2,3-dimethylbutene-1 the operating conditions are purely illustrative and form stream recovery from the eiuent of the double bond no part of the present invention, insofar as the combinaisomerization step is largely converted to propylene and tion process of skeletal and double bond isomerization isobutylene which are readily separable from the neohexis concerned. In this process, the invention resides in the ene in the fractionation zone 28. Finally, I have provided novel combination of isomerization, fractionation and disa novel skeletal isomerization process whereby neohexene proportionation steps. is converted to 2,3-dimethybutcne-2 with excellent yields 35 In a specic example, 95 pounds per hour of neohexene and selectivity. concentrate is charged to the isomerization zone 11 which is operated at a temperature of 600 F., a pressure of l SPECIFIC EXAMPLES AND CONDITIONS atmosphere, and a liquid hourly spaced Velocity of 2.

A broad aspect of the invention relates to the combi- In the fractionation zone 13, 0.5 pound per hour of nation of the described double bond isomerization, skeletal heavy product recovered through the conduit 16 and 0.5 isomerization, disproportionation and fractionation steps pound per hour of heavy product through the conduit utilizing well known disproportionation and isomerization 17, About 5 1b./hr of unchanged neohexene is recovered catalysts for which the operating conditiOIlS, Caalyst and recycled (not shown) to skeletal isomerization zone preparation, regeneration and activation are -Well known 11, 56 pounds per hour of 2,3-dimethy1butene-2 contain. l0 those Skilled in the aft and, hence, need 110i be de- 45 ing a trace of methylpentene is recovered through the scribed in detail herein. The following Table I sets forth line 14. 'Ihe 2,3-dimethylbutene-1 concentrate recovered exemplary catalysts and conditions. through the conduit 15 contains 29 pounds per hour of TABLE I Skeletal Double bond Disproporisomerization isomerization tiouation Zone 11 Zone 18 Zone 24 Catalyst Alumina Palladium (0.05%) Tun sten oxide.

feed. Liquid hourly space velocity-. 0.5-3 Pressure, p.s.i.g 0-200 15-250 Catalyst activation:

Temperature, F. 80G-1,400 150-400 9004.200. Time 0.5-75 hours under 0.1-30 min. in 0.25-5 hr. in air.

nitrogen. hydrogen.

As stated, excellent selectivity and yields are obtained 2,3-dimeth'ylbutene-1, 6 pounds per hour of 2,3-dimethyl- Where the catalyst in the zone 11 is alumina having a butene-Z and 3 pounds per hour of methylpentenes. surface area of 150 to 180 square meters per gram and The isomerization zone is 18 is operated at a tempera sodium oxide content of 0.1 to 0.2 weight percent. This ature of 400 F., a pressure of 1 atmosphere and a liquid is another aspect of the invention. Preferably, this is a hourly space velocity of 2. An alumina catalyst is utilized gamma alumina catalyst. Additionally, this catalyst conin both isomerization zones which has a surface area of tains about 98.0 percent aluminum oxide. It has a bulk 150 to 180 square meters per gram and a sodium oxide density of 0.77 to 0.81 kilogram per liter, a pellet density content of 0.1 to 0.2 weight percent. of 1.26 to 1.33, a true density of 3.6 to 3.7 kilograms From the separation zone 19, 29 pounds per hour of per liter, a porosit'y of 60 to 65 volume percent and a 2,3-dimethylbutene-2 containing a trace of methylpencrushing strength of 15 to 30 pounds. tenes is recovered through the conduit 21, and the` prod- The surface area is conventionally determined by the uct recovered overhead contains 3 pounds per hour 2,3-

so-called BET method described in Journal of American dimethylbutene-2, 12 pounds per -hour 2,3dimethylbutene- Chemical Society 60 309 (1938). Y 75 l and 3 pounds per hour methylpentenes. Half this material is recovered through the line 22, and the rest is passed through the conduit 23 to the zone 18. Where the disproportiouation catalyst zone 24 is utilized, the stream leaving the fractionation zone 19 passes through conduits 22 and 25 to the disproportionation catalyst zone 24, 2,4,4- trimethylpentene-Z is fed to the zone 24 at the rate of 133 pounds per hour and ethylene is fed thereto at the rate of 56 pounds per hour. The zone 24 contains an olefin disproportionation catalyst system comprising 1 part WO3/Si02 and 6 parts mg. O by `weight and is operated at a temperature of 700 F., a pressure of 400 p.s.i.g. and a liquid hourly space velocity of 25 based on the WO3/Si02 catalyst.

From the fractionation zone 28, 95 pounds per hour of neohexene concentrate is recovered and charged to the isomerization zone 11 while 96.3 pounds per hour of light product are discharged through the conduit 29 and 0.5 pound per hour of heavy product through the conduit 30. An isobutylene stream containing 83 pounds per hour is separated from the light product.

The following specic examples in Table II illustrate the conversion of neohexene to 2,3-dimethylbutene-2 utilizing the described high surface area gamma alumina catalyst containing 0.1 to 0.2 weight percent sodium oxide.

TAB LE II Run 1 2 3 4 Temperature, F 604 606 603 601 Pressure, p.s..g 0 2 25 Liquid hourly space velocity. 2. 2 2. 2 4. 5 6. Time in process period, hours... 1 24 29 25 Conversion, wt. percent 95. 3 96. 0 95. 9 92. 6 selectivity to 2,3-dimethylbutene, Wt.

percent 96. 7 95. 6 95. 6 Product composition, Wt percent 0. 1 0. 03 0.02 3,3-dimethylbutene-l. 4. 7 4. 00 4. 13 2,3-dimethylbutene-l 29. 2 29. 70 30. 40 2,3-dimethylbutene-2-. 63. 0 62. 10 61. 30 Neohexane 0. 03 0. 03 3- and 4-methy1pentene-l. 0.09 0. 08 4-methyltranspentene2 0. 49 0. 44 2methylpentene1 0. 99 1. 00 2ethylbutene1- 0.01 0. 01 2-methylpentene-2. 2. 40 2. 43 S-methyl-ciS-pentene-Z. 0. 03 0. 03 3-methyl-trans-pentene-2 0. 08 0. 07 0. 01 O. 01 C-Cir.-. 0. 04 0. 05

Total 100.00 100. 00 100. 00 -00. 00

To further illustrate that the dened gamma-alumina of 0.1 to 0.2 weight percent Nago content, preferably of a surface area of 150 to 180 square meters per gram, represents a uniquely effective and superior catalyst, the following data in Table III is submitted with Run 5 a comparative run with another gamma-alumina:

l TABLE III Isomerization of neohexane to 2,3-dimethylbutenes Run 5 6 7 Catalyst Alumina-- Alumina. Alumina.

Type Gamma..- 1.0 fluoride Gamma.

and chi. NarO, wt. percent-.- .38.

Surface, 111.2 g Conditions:

Temperature, F 605 608 662. Pressure, p.s.i.g. Rate, LHSV Results:

Conversion, percent. selectivity, percent.-.

Data from Pines and Haag, 82 J. A111. Chem. Soc., May 20, 1960, 2,47l2,483, at p. 2,474, experiment 35.

b Slightly less than this due to the fluoriding treatment.

From supplier literature.

6 valuable properties of my particularly defined catalysts in the skeletal isomerization process step I have disclosed in providing both high conversion and high selectivity together.

Other catalysts, even of similar NazO content to my defined catalysts, but which are such as eta-alumina, are nowhere near as effective as my catalysts and do not provide the desired combination of both high conversion and high selectivity. Note particularly in the afore-referenced Pines and Haag article experiments l, 1l, and 19 through 23, using various eta-alumina catalysts of varying Na2O content and surface areas in runs using the same feed and very closely similar conditions to those I have employed. In all such instances, either conversion or selectivity was quite low. My carefully defined catalysts provide both high conversion and high selectivity.

I claim:

1. A process for making 2,3-dimethylbutene-2 which comprises contacting neohexene feed with a skeletal isomerization catalyst at skeletal isomerization conditions, fractionating the resulting etiiuent to provide a 2,3-dimethylbutene-l concentrate containing methylpentenes, and a 2,3-dimethylbutene-2 product, contacting said concentrate with a double bond isomerization catalyst under double bond isomerization conditions, and recovering 2,3- dimethylbutene-Z from the eilluent of the double bond isomerization step; wherein said skeletal isomerization catalyst consists essentially of gamma alumina containing 0.1 to 0.2 weight percent sodium oxide and having a high surface area of about 150 to 180 square meters per gram.

2. In the process of claim 1 recovering a stream containing 2,3dimethylbutenel from the effluent of the double bond isomerization step, and charging said stream to the double bond isomerization zone.

3. A skeletal isomerization process comprising contacting neohexene with a catalyst consisting essentially of gamma alumina having a surface area of 150 to 180 square meters per gram, and a sodium oxide content of 0.1 to 0.2 weight percent, under skeletal isomerization conditions, hereby isomerizing the neohexene to 2,3- dimethylbutene-l.

4. The process of claim 3, wherein the catalyst is activated under nitrogen at a temperature of 800 to 1400 F. and a time of 50 to 75 hours.

5. The method of claim 4 wherein the skeletal isomerization process is operated at a temperature within the range of 500 to 800 F., a pressure of atmospheric to 200 pounds per square inch gauge and a liquid hourly space velocity of 0.5 to 30.

6. A process for making 2,3-dimethylbutene-2 which comprises:

(a) contacting neohexene feed with a skeletal isomerization catalyst under skeletal isomerization conditions,

(b) fractionating the resulting eiuent from said contacting step (a) to provide a 2,3-dimethylbutene-l concentrate further containing methylpentenes, and a first 2,3-dimethylbutene-2 product stream,

(c) contacting said concentrate from said step (b) with a double bond isomerization catalyst under double bond isomerization conditions,

(d) recovering from the eflluent from said step (c) a second 2,3-dimethylbutene-2 product stream, and a fraction containing 2,3-dimethylbutene-1 further containing methylpentenes,

(e) disproportionating said fraction containingZ-dimethylbutene-l and methylpentenes together' with ethylene and 2,4,4-trimethylbutene-2 under disproportionation conditions,

(f) recovering from the eluent of said step (e) an isobutylene stream and a neohexene feed, and

(g) employing said neohexene feed in said step (a).

7. In the process of claim 6 further: recovering a stream containing 2,3-dimethylbutene-1 from the eiiiuent of said double bond isomerization step (c) and charging said 2,3-dimethylbutene-1containing stream to said double bond isomerization step (c).

8. The process of claim 7 further: dmerizing under dimerization conditions at least a portion of said isobutylene to said 2,4,4-trimethylpentene-Z.

9. The process of claim 8 wherein said skeletal isomerization catalyst in said step (a) consists essentially f gamma alumina having a sodium oxide content of 0.1 to 0.2 weight percent.

10. The process according to claim 9 wherein said skeletal isomerization gamma alumina catalyst is further characterized as having a surface area of 150 to 180 square meters per gram.

11. The process of claim 9 wherein the skeletal isomerization gamma alumina catalyst has a surface area of 150 to 180 square meters per gram; and the skeletal isomerization conditions are a temperature of 500 to 800 F., a liquid hourly space velocity of 0.5 to 30, a pressure of 0 to 200 pounds per square inch gage, a catalyst 20 activation temperature of 800 to 1400 F. and a catalyst activation time of 0.5 to 75 hours under nitrogen, the double bond isomerization catalyst is palladium on alumina, and the double bond isomerization conditions are a temperature of to 450 F., a liquid hourly space velocity of 0.5 to 30, a pressure of 15 to 250 pounds per square inch gage, the catalyst activation temperature is to 400 F., the catalyst is activated for 0.1 to 30 minutes in hydrogen, and 0.03 to 0.1 mole of hydrogen is fed to the double bond isomerization zone per mole of olen feed.

References Cited UNITED STATES PATENTS ID-ELBERT E. GANTZ, Primary Examiner V. OKEEFE, Assistant Examiner U.S. Cl. X.R. 260-683 D UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No., 3,781,377 John w- Myers Umm December 25, 1973 It is certified that error appears in the bever-identzLzi'fLedV patent and that said letters Patent are hereby corrected as shown below: e

claim 11, column 7, line 1, "9"l shouldbe 6..

Signed and sealed the 18th day of June 1971;;

(SEAL) Attest:

c. MARSHALL DANN.

v'EDwARDMJIETCHER,.117'. l v y Attesting' Officer -1 l `Gcbxm'nisssomer of Pate'lrxtsxl f/ 

